Biochemical Characterisation of an Epitope on the Surface Membrane Antigen (Cs-gp200) of the Pathogenic Piscine HaemoflagellateCryptobia salmositicaKatz 1951

Abstract

A protective surface antigen (200 kDa) onC. salmositicawas detected using a monoclonal antibody (mAb-001). Enzymatic studies on the epitope indicated that it was sensitive to nonspecific protease K and to site-specific trypsin and protease V8 but not to α-chymotrypsin. The reactivity of the epitope with mAb-001 was not affected when the antigen was denatured with 8Murea; however, reduction of the antigen with dithiothreitol destroyed the epitope. The epitope was susceptible to sodiumm-periodate oxidation andN-glycosidase F, but not toO-glycosidase or neuraminidase. It was also sensitive to mild potassium hydrochloride hydrolysis and to phospholipase C, which is specific for phosphatidylinositol. These results suggest that the epitope consists of a polypeptide, a carbohydrate, and probably a phospholipid. The asparagine-bound N-glycosidically linked hybrid-type carbohydrate chain has the minimum length of a chitobiose core unit. There is probably a phosphatidylinositol residue which anchors the polypeptide to the surface membrane. The antigen is extensively posttranslationally modified.